The present invention relates to pneumatic radial tires for passenger cars, and particularly relates to tires which are contrived to prevent hydroplaning and reduce noise by having a unique tread pattern.
In the prior art, rib-lug type tire, many of ribs are generally formed between several circumferential grooves formed along the middle of the tread and several generally axial grooves which have a certain slant angle to those circumferential grooves form numerous lugs in a certain pitch.
Tires with such rib-lug type tread pattern do not have quiet-smooth driving as a result of its contact with the ground. The contact between tire and ground traps air inside of above-mentioned circumferential grooves and the air is compressed. As this process takes place repetitiously it yields the high frequency noise, approximately 1 KHz, thus, such phenomenon becomes severe during high-speed driving or under heavy load.
In order to reduce such noise, conventional tires tried to change the pitch of lug or width of grooves, but this effort was not effective to mitigate the air pumping noise caused by constant air flow process of trapping, compressing and releasing. Also, as a concomitant phenomenon, inappropriate juxtaposition of ribs and/or lugs resulted in applying concentrated load on a particular area which led to biased abrasion or abnormal abrasion.
As one of the objectives of the present invention, it is to provide tire tread pattern reducing air pumping noise without accompanying biased abrasion or abnormal abrasion of ribs and/or lugs.
On the other hand, tread pattern which is distinguished by grooves and/or sipes releases water as tire is utilized during rainy weather or on damp road surfaces, beside providing braking and/or ground gripping power. However, if water trapped inside of grooves is not promptly and sufficiently released or dispersed, it could jeopardize safe driving of the vehicle by causing hydroplaning. Accordingly, designing of tire tread pattern needs to be done to provide improvement of anti-hydroplaning and wet road performance beside reducing of noises.
Therefore, another objective of the present invention is to provide a tire tread pattern which will prevent tires from causing hydroplaning when they are utilized on wet road surface or in rainy weather.
In order to accomplish above mentioned first and second objective of the present invention, as the distinctive features of the invention, the tire manufactured according to the present invention has circumferential grooves and several generally axial grooves capable of inducing and releasing trapped air therein sufficiently through the grooves by allocating equal ground contact pressure to ribs and/or lugs. Also, the tread pattern according to the present invention forms characteristically a number of auxiliary grooves on a ground contacting surface of the tread in order to release or disperse the remaining exceeding water from main grooves through above mentioned auxiliary grooves.
The other unique and advantageous features of the present invention can be better perceived in the following detailed description of the invention.